Apparatuses, systems and methods for tilling agricultural fields are very well known in the art. Apparatuses typically comprise a cultivator frame having multiple and various tilling attachments attached thereto, laid out on the frame in a variety of patterns to maximize the desired tilling effect. The apparatus is dragged behind a vehicle during the tilling operation.
In particular, conservation tillage, or vertical tillage as it is sometimes called, has recently become a tilling strategy of choice in many instances. Conservation tillage minimally disturbs the soil prior to planting in order to allow air to penetrate the mat of crop residue left in the field from the previous harvest. Apparatuses, systems and methods for conservation tillage are known in the art, for example U.S. Pat. No. 7,762,345 issued Jul. 27, 2010, U.S. Pat. No. 8,113,295 issued Feb. 14, 2012, U.S. Pat. No. 8,196,672 issue Jun. 12, 2012, U.S. Pat. No. 8,307,908 issued Nov. 13, 2012 and U.S. Pat. No. 8,307,909 issued Nov. 13, 2012, the entire contents of all of which are herein incorporated by reference.
In addition to coulter wheels, chisel plows, V-shaped shovels, sub-soiling teeth and other field working tools, a tillage apparatus may comprise leveling attachments at the rear of the cultivator frame. The leveling attachments may be mounted to a rear transverse cross-member of the frame. Leveling attachments may comprise, for example, spike harrows, leveling bars, rotary harrows, etc., which are dragged behind the cultivator frame to level the field after the field is worked by the field working tools.
A conservation tillage apparatus may be drawn at faster speeds than conventional tillage apparatuses. Although there is no theoretical upper limit on speed, conservation tillage apparatuses may be operated at speeds of from 8-18 miles per hour. Operating at such faster speeds causes the crop residue to be cut more finely and reduces the likelihood of becoming stuck in wet soil conditions. However, operating at faster speeds, especially above 12 miles per hour, can create significant problems and damage when leveling attachments being dragged behind the cultivator frame encounter a hard impediment, such as a rock. This is especially true for rotary harrows.
Harrows are implements comprising sets of teeth, tines or ridges that when dragged over ploughed land break up clods, remove weeds, and cover seed. A rotary harrow is a harrow with one or more turning wheels or drums rimmed with spikes or ridges. The turning wheels or drums are mounted in a relatively long basket. The basket of the rotary harrow is typically immovably mounted to a rear transverse cross-member of the cultivator frame. When a rotary harrow hits a hard impediment, the point of impact will be a relatively localized point along the entire length of the harrow. The impact will cause the harrow to deflect upwards at this point. In addition to translating upwards applying forces or stresses against the immovable mounting, the deflection will cause the relatively long harrow to pivot or twist around an axis causing the harrow to twist against its mountings. At high speeds, the upward and twisting forces caused when the harrow hits the hard impediment can be large enough to damage the harrow, the cultivator frame or both.
Some attempts have been made to overcome this problem. U.S. Pat. No. 7,766,093 issued Aug. 3, 2010, the entire contents of which is herein incorporated by reference, describes a hydraulically lift rolling basket structure for a tillage implement. The rolling basket structure includes an arm structure pivotally connected to the aft end of tine support members fixed to the rear of the implement frame. Hydraulic cylinders connected between the support members and the arm structure provides quick on-the-go disengagement of the rolling basket with the ground, for example, when wet or sticky ground conditions or the like are encountered. A cylinder lost motion connection facilitates movement of the baskets over ground irregularities and obstacles without operation of the cylinders. In this arrangement, the hydraulic cylinders may be actuated to raise the rolling basket over wet ground and the lost motion connection permits upward motion of the entire rolling basket when any part of it encounters a hard impediment. The lost motion connection comprises a pin in a curved slot that allows some vertical play over the entire length of the basket when it encounters a hard impediment. However, because the entire basket is raised when a hard impediment is encountered, the rotary harrow will fail to level significant areas of the field due to the impact of relatively small hard impediments.
There remains a need for means of reducing damage to a rotary harrow and/or cultivator frame when the harrow encounters a hard impediment in a field while being dragged behind a tillage apparatus, while at the same time maximizing the effectiveness of the harrow at leveling the field.